Mechanisms involved in hydrocarbon-induced transformation will be studied in an in-vitro model for chemical carcinogenesis which employs fibroblasts derived from mouse prostate that are susceptible to hydrocarbon-induced malignant transformtion. The metabolism-dependence of transformation induced by 7, 12-dimethylbenz(a)anthracene will be investigated by comparing its transforming activity with that of different known metabolites, particularly the K-region epoxide. The possible cell-cycle dependence of hydrocarbon-induced transformation will also be studied. For this purpose transformable cells will be synchronized and treated during various phases of the mitotic cycle with short-lived transforming agents such as hydrocarbon K-region epoxides. The increase in DNA synthesis caused by the transforming agent, the K-region epoxide of benzanthracene, may be a significant biochemical event in transformation. It is planned to determine whether the increase is semiconservative replication or unscheduled, "repair" synthesis. Finally, treatment of hydrocarbon-transformed cell lines by 5- bromodeoxyuridine (BUdR) has resulted in the indution of variants with decreased malignancy. It is to be determined whether the mechanism involved in "BUdR reversion" is dependent on DNA synthesis and whether cell membrane functions are altered in "reverted" cells.